rs1555598687

chr17-80104827-C-T

Variant summary

Our verdict is Pathogenic. Variant got 18 ACMG points: 18P and 0B. PVS1 PM2 PP5_Very_Strong

The NM_000152.5(GAA):c.241C>T(p.Gln81Ter) variant causes a stop gained change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.00000137 in 1,460,238 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a pathogenic outcome for this variant. Variant has been reported in ClinVar as Pathogenic (★★★). Variant results in nonsense mediated mRNA decay.

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 0.0000014 (0 hom.)
• Consequence: GAA NM_000152.5 stop_gained
• Clinical Significance: Pathogenic reviewed by expert panel P:3
• Conservation: PhyloP100: 0.333

Genes affected

GAA (HGNC:4065): (alpha glucosidase) This gene encodes lysosomal alpha-glucosidase, which is essential for the degradation of glycogen to glucose in lysosomes. The encoded preproprotein is proteolytically processed to generate multiple intermediate forms and the mature form of the enzyme. Defects in this gene are the cause of glycogen storage disease II, also known as Pompe's disease, which is an autosomal recessive disorder with a broad clinical spectrum. Alternative splicing results in multiple transcript variants. [provided by RefSeq, Jan 2016]

ACMG classification

Verdict is Pathogenic. Variant got 18 ACMG points.

• PVS1: Loss of function variant, product undergoes nonsense mediated mRNA decay. LoF is a known mechanism of disease.
• PM2: Very rare variant in population databases, with high coverage
• PP5: Variant 17-80104827-C-T is Pathogenic according to our data. Variant chr17-80104827-C-T is described in ClinVar as [Pathogenic]. Clinvar id is 557360.Status of the report is reviewed_by_expert_panel, 3 stars. Variant chr17-80104827-C-T is described in Lovd as [Pathogenic]. Variant chr17-80104827-C-T is described in Lovd as [Pathogenic].

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
GAA	NM_000152.5	c.241C>T	p.Gln81Ter	stop_gained	2/20	ENST00000302262.8

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
GAA	ENST00000302262.8	c.241C>T	p.Gln81Ter	stop_gained	2/20	1	NM_000152.5	P1

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome AF: 0.00000137 AC: 2 AN: 1460238 Hom.: 0 Cov.: 31 AF XY: 0.00000275 AC XY: 2 AN XY: 726448

Gnomad4 AFR exome AF: 0.00

Gnomad4 AMR exome AF: 0.00

Gnomad4 ASJ exome AF: 0.00

Gnomad4 EAS exome AF: 0.00

Gnomad4 SAS exome AF: 0.00

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 0.00000180

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 32

ClinVar

Significance: Pathogenic

Submissions summary: Pathogenic:3

Revision: reviewed by expert panel

Submissions by phenotype

Glycogen storage disease, type II Pathogenic:3

Likely pathogenic, criteria provided, single submitter	clinical testing	Counsyl	Mar 20, 2018	- -
Pathogenic, criteria provided, single submitter	clinical testing	Invitae	Sep 13, 2019	This sequence change creates a premature translational stop signal (p.Gln81*) in the GAA gene. It is expected to result in an absent or disrupted protein product. This variant is not present in population databases (ExAC no frequency). This variant has been observed in an individual glycogen storage disease type II (PMID: 25526786). ClinVar contains an entry for this variant (Variation ID: 557360). Loss-of-function variants in GAA are known to be pathogenic (PMID: 18425781, 22252923). For these reasons, this variant has been classified as Pathogenic. -
Pathogenic, reviewed by expert panel	curation	ClinGen Lysosomal Storage Disorder Variant Curation Expert Panel	Jun 15, 2020	This variant, c.281C>T (p.Gln81Ter), is a nonsense variant which is predicted to cause nonsense mediated decay and lack of gene product, meeting PVS1. The variant is absent in gnomAD v2.1.1, meeting PM2. Three siblings, all with low residual GAA activity meeting PP4, were reported to be compound heterozygous for the variant and a pathogenic missense change, c.2238G>C (p.Trp746Cys) (PMID 25526786). However, the intrans data was used in the assessment of p.Trp746Cys and was not included here in order to avoid a circular argument. There is a ClinVar entry for this variant (Variation ID: 557360, 1 star review status) with one submitter classifying the variant as likely pathogenic. In summary, meets the criteria to be classified as pathogenic for Pompe disease. GAA-specific ACMG/AMP criteria applied, based on the specifications of the ClinGen LSD VCEP: PVS1, PM2, PP4. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
BayesDel_addAF	Pathogenic	0.63	D
BayesDel_noAF	Pathogenic	0.47
Cadd	Pathogenic	35
Dann	Uncertain	1.0
Eigen	Uncertain	0.27
Eigen_PC	Benign	0.00084
FATHMM_MKL	Benign	0.18	N
MutationTaster	Benign	1.0	A;A
Vest4		0.56, 0.56
GERP RS		2.8

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.010		Details are displayed if max score is > 0.2

Find out detailed SpliceAI scores and Pangolin per-transcript scores at spliceailookup.broadinstitute.org

Publications

LitVar

Other links and lift over

dbSNP: rs1555598687; hg19: chr17-78078626;